JPS61170614A - Electric signal-air pressure conversion unit - Google Patents

Abstract

PURPOSE:To control an air pressure by using a pressure sensor with high accuracy by acting the pressure of a control object such as pressure tank as a direct feedback signal to a pressure sensor. CONSTITUTION:The free end of a nozzle flapper mechanism 22 consisting of an electrostrictive element 24 is displaced in the direction where a nozzle 18 is closed when the voltage to be impressed to said mechanism increases. The quantity of the air ejected from the nozzle 18 is thereby decreased and the pressure in a nozzle back pressure chamber 16 is increased. This pressure acts atop an upper diaphragm 30. As a result, the equil. state is broken and the upper diaphragm 30 and a lower diaphragm 32 descend. An exhaust valve 34 and an inside valve 36 formed integrally therewith descend. An air feed port 53 is therefore opened and part of the supply pressure from a supply port 38 is supplied to an output port 52. The output air pressure thus formed is supplied to a pressure tank 63, by which the intended function is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrical signal-to-pneumatic conversion unit that converts an electrical signal into fluid pressure, particularly air pressure, and more specifically, the present invention relates to an electrical signal-to-air pressure conversion unit that converts an electrical signal into fluid pressure, particularly air pressure, and more specifically, it electrically feeds back output air pressure to the input side via a pressure sensor. The present invention relates to an electrical signal-to-pneumatic conversion unit configured to perform.

Conventionally, a nozzle flapper using a torque motor has been widely used as a device for converting an electric signal into a pneumatic signal. That is, according to this type of nozzle flapper,
A current is supplied to a coil constituting a torque motor, and a rotational force corresponding to the current value changes the swing angle of the flapper, thereby controlling the nozzle back pressure, that is, the output. Therefore, a change in the drive current supplied to the torque motor appears as a change in the pneumatic output. Therefore, in such an electric signal/pneumatic pressure converter, the output pneumatic pressure is fed back to the input side so that the output pneumatic pressure faithfully responds to the input signal of the torque motor.

A typical block diagram of an electrical signal-pneumatic converter using this feedback system is shown in FIG. In FIG. 1, reference numeral a indicates a torque motor, and the output of the torque motor a is configured to control the nozzle back pressure of the nozzle flapper mechanism C via a summing point. The output side of the nozzle flapper mechanism C outputs predetermined pressure air via the pilot valve section d. On the other hand, this output air pressure is fed back to the feedback element e, and the output side of the feedback element e is connected to an addition point so that its output functions as a subtraction element.

In this case, a force-balanced feedback element such as a bellows or a diaphragm is generally used as the feedback element.

By the way, a case will be described in which the air pressure is controlled using the electrical signal-air pressure converter configured as described above. The block diagram in Figure 2 shows an example of this. Air is used on the load side, and electrical signal-pneumatic converter f is connected to the load side so that the source pressure does not change much even if the air flow rate fluctuates. A pressure tank g is interposed in the connecting circuit, and the air pressure is controlled by the electrical signal-air pressure converter f so that the air pressure in the pressure tank g is constant. In addition, in the figure, reference numerals indicate pneumatic piping.

However, as mentioned above, in this type of device,
The electric signal/pneumatic pressure converter f feeds back the output air pressure immediately after passing through the pilot valve section d to the addition point within the device.

Therefore, if the electrical signal-to-air pressure converter f and the pressure tank g are connected by a relatively long pneumatic piping, and if the pressure tank g is connected to the load side and air is used, then the electrical signal - Significant differences occur between the side pressures in parts close to the load, such as in the pressure tank g immediately after the outlet of the pneumatic transducer f, and therefore in the pilot valve part d.
There is a disadvantage that accurate control cannot be achieved even if the output air pressure immediately after is used as a feedback signal.

Therefore, as a result of intensive research and ingenuity, the inventor of the present invention found that
A pressure sensor for detecting output air pressure as an electric signal is attached to the converter body, and a passage is provided for applying air pressure to the pressure sensor from outside the conversion unit body, and the detection signal of the pressure sensor is converted into an electric signal. - If the controller is configured to input as a feedback signal to the input signal to the pneumatic pressure conversion element, an electric signal-pneumatic conversion unit can be obtained that can directly extract the internal pressure of a controlled object such as a pressure tank as a feedback signal. It was found that the above-mentioned inconveniences were eliminated.

Therefore, an object of the present invention is to provide an electrical signal-pneumatic pressure conversion unit that can perform highly accurate pneumatic pressure control by obtaining a feedback signal directly from a controlled object.

In order to achieve the above object, the present invention includes a nozzle flapper mechanism that changes the nozzle back pressure according to the amount of displacement of the nozzle flapper in the main body of the electrical signal-pneumatic conversion unit, and a diaphragm that responds to the nozzle back pressure to connect the supply port and the output. In an electrical signal-to-air pressure conversion unit that incorporates a pilot valve that controls the output air pressure by opening and closing an inner valve provided at an air supply port that connects ports, fluctuations in air pressure are detected as electrical signals in the conversion unit body. A controller is provided that includes a pressure sensor, connects a passage for applying output air pressure from outside the conversion unit main body to the pressure sensor, and inputs the detection signal of the pressure sensor as a feedback signal to the input signal to the nozzle flapper. It is characterized by

Next, preferred embodiments of the electrical signal-pneumatic conversion unit according to the present invention will be described in detail with reference to the accompanying drawings.

In FIG. 3, reference numeral 10 indicates an electrical signal-to-pneumatic conversion unit main body, and this conversion unit main body 10 includes a nozzle flapper mechanism 12 provided in the upper part of the interior thereof and a pilot valve section 14 provided in the lower part of the interior thereof.

The nozzle flapper mechanism 12 includes a pilot valve section 1 which will be described later.
It is composed of a nozzle 18 of a predetermined diameter communicating with the nozzle back pressure chamber 16 of No. 4, and a plate-shaped nozzle flapper mechanism 22. One end of the nozzle flapper mechanism 22 is positioned as a free end with a predetermined distance from the nozzle 18, and the other end is fixed to the conversion unit main body 10 via a screw 20. As shown in FIG. 4, the nozzle flapper mechanism 22 includes two piezoelectric ceramics 2 provided with electrodes.
4.24 and an electrode plate 26 sandwiched between these piezoelectric ceramics 24.24, which is a so-called electrostrictive element, and lead wires 28.28 connected to each of these piezoelectric ceramics 24.24. A predetermined voltage is applied from the controller 29 via the controller 29.

On the other hand, the pilot valve section 14 includes two diaphragms 30.32 arranged vertically in parallel, and an exhaust valve 34 and an inner valve 36 interlocked with these diaphragms 30.32. The exhaust valve 34 is substantially connected to the diaphragm 30.
．． It consists of a cylindrical body formed at the lower end of a locking member 33 that holds the inner valve 32 apart for a predetermined distance, and a part of the inner valve 36 can be seated on this cylindrical body, as will be described later. Note that the inner valve 36 has an air supply valve section 36a and an exhaust valve section 3.
6b.

On the other hand, a supply port 38 is defined on one side of the conversion unit main body 10, and passages 40a, 40b, 40c, 40d, and 40e communicate with each other from the middle of the supply port 38 and extend to the nozzle back pressure chamber 16. Exists.

At this time, a fixed orifice 44 is interposed in the passage 40d located on the downstream side, and a supply hole defined by the upper diaphragm 30 and a smaller lower diaphragm 32 whose effective area is slightly smaller than that of the upper diaphragm 30 is provided. Pressure chamber 4
6, a passage 40f branched from the passage 40b located on the upstream side described above is connected to communicate with the passage 40f, and supplies pressurized air from the supply port 38 to the supply pressure chamber 46. Furthermore, an atmospheric pressure chamber 48 is defined below the lower diaphragm 32;
It is configured so that the atmosphere is directly introduced through a passage (exhaust port) 50. Note that in the figure, reference numeral 52 indicates an output port.

In this case, the inner valve 36 is arranged so as to close the air supply port 54 connecting the supply port 38 and the output port 52 when the above three pressures, that is, nozzle back pressure, supply pressure, and atmospheric pressure are balanced, Furthermore, at this time, the exhaust valve portion 36b constituting the inner valve 36 engages with a valve seat 60 formed on the exhaust valve 34, and opens the exhaust passage 58 that reaches the atmospheric pressure chamber 48 via the valve seat 60. Configured to be occluded. Therefore, it is easily understood that this pilot valve section 14 is a non-bleed type in which exhaust is not performed during equilibrium.

Further, an O-ring 64 is interposed in the passage 62 through which the exhaust valve 34 is displaced, and a recess 68 is defined above the inside of the conversion unit main body 10. And this recess 68
A pressure sensor 66 is fitted and fixed to. This pressure sensor 6
6 includes a semiconductor diaphragm (not shown) inside, and the displacement of this semiconductor diaphragm is extracted as a voltage displacement.

That is, the value of electrical resistance changes due to the displacement of the diaphragm, and this is used to detect the output pressure as an electrical signal. Therefore, a passage 70 is bored inside the conversion unit main body 10, and one end of this passage 70 is connected to the recess 68.
It communicates with the inside of the pressure sensor 66 through a bottom space 68a, and the other end communicates with the outside through an opening formed with a tapered screw 72.

Therefore, if the inside of the pressure sensor 66 is communicated with a pressure tank 63 (described later) via a passage 70 and a pipe (not shown) connected to this passage 70, the pressure inside the pressure tank 63 can be detected by the pressure sensor 66. It will be understood that the detection signal is inputted to the controller 29 via the lead wires 74 and 74. In FIG. 3, reference numeral 80 indicates a coil spring that normally biases the inner valve 36 in the valve-closing direction.

FIG. 5 shows a block diagram showing the control system of the electrical signal-to-air pressure conversion unit configured as described above. That is, the first amplifier circuit 82 is connected to the output side of the controller 29, and the output side of this first amplifier circuit 82 is connected to the nozzle flapper mechanism 22. The nozzle flapper mechanism 22 derives its output to control the pilot valve section 14, and the pilot valve section 14 supplies pressurized air at a predetermined pressure to the pressure tank 63. On the other hand, the pressure in the pressure tank 63 is detected by the sensor 66 and sent to the second amplifier circuit 84, and the output signal and input signal of this amplifier circuit 84 are combined at a summing point (not shown) in the controller 29. They are matched to form an output signal.

The electrical signal-pneumatic pressure conversion unit according to the present invention is basically constructed as described above, and its operation and effects will be explained next.

Now, when the voltage applied to the nozzle flapper mechanism 22 made of an electrostrictive element increases in a state where the system is in equilibrium as shown in FIG. 3, the free end of the nozzle flapper mechanism 22
8 in the direction of closing.

As a result, the amount of air ejected from the nozzle 18 decreases, so the pressure in the nozzle back pressure chamber 16 (nozzle back pressure) increases, and this pressure acts on the upper surface of the upper diaphragm 30.

As a result, the equilibrium state of the system is disrupted, the upper diaphragm 30 and the lower diaphragm 32 descend, and as a result of this descending action, the exhaust valve 34 integrally formed therewith and the inner valve 36 interlocked with the exhaust valve 34 descends. For this reason,
The air supply port 54 is opened, and part of the supply pressure from the supply port 38 becomes output air pressure and is supplied to the output port 52. This output air pressure is supplied to the pressure tank 63 to perform the intended function.

At this time, in this embodiment, as described above, the passage 62 through which the exhaust valve 34 is displaced is hermetically sealed by the O-ring 64, and the lower side of the lower diaphragm 32 is always open to the atmosphere, so that the output air pressure is lower than the lower diaphragm 32. Since the configuration is such that no feedback is provided to the diaphragm 32, the pressure gain between the nozzle back pressure and the output air pressure becomes very large. As a result, even a slight change in nozzle back pressure results in a significant change in output air pressure.

Next, in the above state, the inner valve 36 moves downward and the air supply port 54 remains open, but in reality, as described above, the pressure sensor 66 detects the pressure inside the pressure tank 63 corresponding to the output air pressure. The pressure is fed back to the input side as an electrical signal. That is, as shown in FIG. 5, the pressure in the pressure tank 63 into which the output air pressure from the pilot valve section 14 is introduced is detected as an electrical signal by the pressure sensor 66, and this detection signal is sent to the controller via the amplifier circuit 84. 29 is fed back. Then, the controller 29 compares the signal with the input signal to the electrical signal-pneumatic conversion unit main body 10, and the deviation thereof is sequentially amplified by the amplification circuit 82 and applied to the electrostrictive element constituting the nozzle flapper mechanism 22. Ru. As a result, the nozzle back pressure changes in accordance with the deviation, and this control is performed continuously. In this way, when the output air pressure matches the input signal, the nozzle back pressure returns to its original state, which causes the inner valve 3
6 also returns to its original state, closing both the air supply port 54 and the valve seat 60, and a new equilibrium state is obtained.

Next, FIG. 6 is a block diagram showing an example of application of the electrical signal-pneumatic conversion unit according to the present invention. In addition, in the figure,
The same reference numerals as in the previous embodiment indicate the same components.

This application uses a pneumatic booster relay. That is, the conversion unit main body 10 in the above embodiment
The output air pressure of the booster relay 90 is applied as a pilot signal to the pneumatic booster relay 90, and the output air of the booster relay 90 is guided to the pressure tank 63.

According to such a configuration, since the foot bank signal is extracted from the pressure tank 63' as in the previous embodiment, good control results can be obtained even if the pneumatic booster relay 90 is not highly accurate. Moreover, even if the capacity of the conversion unit main body 10 is small, if there is a large capacity pneumatic booster relay 90, there is an advantage that the capacity is large and moreover, the air pressure can be controlled with high precision.

As explained above, according to the present invention, the pressure of a controlled object such as a pressure tank is configured to act on the pressure sensor as a direct feedback signal. Even if the air pressure sensor is connected by piping, it is possible to control the air pressure with high precision using a pressure sensor.

Although the present invention has been described above with reference to preferred embodiments, the present invention is not limited to these embodiments, and various improvements and changes in design can be made without departing from the gist of the present invention. Of course.

[Brief explanation of drawings]

FIG. 1 is a block diagram of feedback control of an electric signal to pneumatic converter according to the prior art, FIG. 2 is a block diagram showing an application example of the electric signal to pneumatic converter, and FIG. 3 is a block diagram of feedback control of an electric signal to pneumatic converter according to the present invention. A longitudinal sectional view of the signal-pneumatic conversion unit, FIG. 4 is an explanatory diagram of the main part of the flapper mechanism incorporated in the conversion unit of FIG. 3, and FIG. 5 is a block line for performing feedback control of the conversion unit of FIG. 3. FIG. 6 is a block diagram showing an application example of the electrical signal-pneumatic pressure conversion unit according to the present invention. 10... Conversion unit main body 12... Nozzle flapper IH1 14... Pilot valve part 16... Nozzle back pressure chamber 18
... Nozzle 20 ... Screw 22 ... Nozzle flapper mechanism 24 ... Piezoelectric ceramic 26 ... Electrode plate 28 ... Lead wire 29 ... Controller 30. 32 ... Diaphragm 33 ... Locking member 34 ... Exhaust valve 36
・・Inner valve 38・・Supply port) 40a to 40f
... Passage 44 ... Fixed orifice 46 ... Supply pressure chamber 48 ... Atmospheric pressure chamber 5o ... Passage 52 ... Output port 54 ... Air supply port 58 ... Exhaust passage 6o ... Valve seat 62 ... Passage 63・・Pressure tank 64・・OIJ ring 66・・Pressure sensor 68・・Recessed part
7o...Passage 72...Tapered screw 74...
Lead wire 80...Coil spring 82.84...Amplification circuit 90...Booster relay

Claims (2)

[Claims] (1) A nozzle flapper mechanism that changes the nozzle back pressure according to the amount of displacement of the nozzle flapper is installed in the electrical signal-air pressure conversion unit body, and an air supply port that connects the supply port and the output port with a diaphragm that responds to the nozzle back pressure. In an electrical signal-pneumatic conversion unit that incorporates a pilot valve section that controls the opening and closing of an inner valve to control output air pressure, a pressure sensor that detects fluctuations in air pressure as an electrical signal is installed in the conversion unit body, and the pressure An electrical signal-air pressure system, characterized in that it is provided with a controller that communicates and connects a passage for applying output air pressure from outside the conversion unit main body to the sensor, and inputs the detection signal of the pressure sensor as a feedback signal to the input signal to the nozzle flapper. conversion unit. (2) The electrical signal-to-pneumatic conversion unit according to claim 1, wherein the pressure sensor is connected via a pipe line so that the pressure of an external control target acts directly on the electrical signal-to-pneumatic conversion unit.